Dyeing of chamois-leather



Patented Jan. 12, 1932 UNETD HEINRICH BRUNNER, OF BASEL, SWITZERLANTJQASSIG ITOR' TU THE FIRM-WHEIIIGAL WORKS FORMER/LY SANDOZ, OF BASED; SWITZERLAND DYEING or CHAMOIS-LEATHER' are Drawing. Application filed December 24, 1928, Serial No. aaasrz, and in -Germany-lanuaxy'e; are.

Up to recently shades on chamois-leather, which are fast to washing, could only be obtained with dye-wood extracts of which the scale of shades is a very limited one. Besides the dilferent grey and brown shades no comparatively fast dyeings could be obtained; more particularly the fastness to soaping was not satisfactory.

Recently various trials have been undertaken with the object to obtain soap proof and otherwise fast shades with sulphur dyes. The dyeing with sulphur dyes requires alkalis of such a concentration that an injuriy I leather representsa technical progress.

' The following examples illustratef the I.

ous effect on the skin cannot be avoided.

The chamois-leather dyed with vat and sulphur dyes is, with regard to its characteristic properties, such as touch and elasticity, so considerably altered that these methods did not find any acceptance.

Other processes are known, according to which the injurious action of the'alkalis has been reduced by the addition of protective colloids (glucose, gelatine, soaps) or substances of similar action such as glycerine,

. formaldeh de sul )hite cellulose waste, where y a l the formaldehyde especially acts in ahardening manner. By the use of these methods, the above mentioned characteristic properties of chamois-leather could not be maintained, especially when the leather has been dyed with vat and sulphur dyes.

It has now been found that by a pretreatment of chamois-leather with appropriate inorganic oxidizing agents as well as with similarly acting organic substances, the dyeing operation can be so considerably accelerated that the dyeing is finished before the al- -kalis have been able to act in an injurious manner on the leather. As inorganic oxidizing agents the following enter into consideration: hydrogen peroxide, perborates or halogens, and among organic substances the halogen acylamids (chloramines) may be useful. Chamois-leather dyed in this manner conserves its characteristic properties such as touch and elasticity, and the dyeings thus obtained are level and fast to washing and soaping. The alkali sulphide necessary for dyeing with sulphur dyes is evidently partially oxidized on the leather and the dyestuff is fixed. "lt is not necessary to the skins to fair in order to oxidize the yeistuffs.

To finish the dyeing and for bright shades it. may be advantageous to subject the dyeings' to an aftertre'atment in an oxidizing bath, -co'ntaining,"forfinstance, acid reacting inorganic oxidizing agents, such as alkali bichromates'or another acid or neutral which anacidulatdalkali'metal nitrite'solirprovedjprocess." Example 1. 1,0 g'. ofchamoisleather are thoroughly washed, if necessary with {som alkali or soap. Thereupon'jthejleatlferfli's milled in a'solution of 5 of metal perborate in 3 litres of water during anhour and subsequently squeezed out and shortly rinsed.

Afterwards 6 g. of thional green B(Col o'ur Index No. 1006) and the necessary quantity metal salt "solution. ojr oxidizing'properties of of sodium sulphide are dissolved in 2 litres of water and the leather dyed in a closed dyeing apparatus. After 20-30 minutes the dyebath is exhausted. The leather is then squeezed out and afterwards subjected to an aftertreatment by handling it in a watery solution containing 2 g. of sodium bichromate and 5 g. of concentrated acetic acid. Thereupon the leather is rinsed and soaped'.

Example 100 g. of Chamois-leather are thoroughly cleaned and afterwards treated with a mixture of 25 com. of a cl'e'arh'ypm chlorite of lime solution in'3flitres of water, whereupon the hypo chlorite reaction disappears rather quickly from the solution. 7 At the same time the smell cannot be observed'anymore. The leather is afterwards hydroextracted and can then be brought'into the dyebath containing-6 g. of thional indon blue R, (Colour .Indexv No. 959) and'6 g. of anhydrous sodium sulphide; When the bath is exhausted, the leather is pressed out, hydroextracted and aftertreated with a bichromate solution as indicated in Example 1.

chamois-leather are handled in 3 litres of water containing 2 g. of the sodium salt of p-toluene sulphonic chloramide, whereupon it is possible to regulate the gradual setting 5 free of chlorine by a slow addition of diluted or weakacids, After a suflicient treatment *.j- V

with a watery solution of2 g.'-o'f'"acetic acid, the leather is pressed, shortly rinsed and dyed t ll a bath containing g. oft-.th ional black '1. (C01our =--ll9.:9, 8)' nd 135% 019753;?-

hydrous sodium sulphide. After half an hour of dyeing no increase inithe depth Ofhli. the tone is obtained, whereupon the afteroxidation "withbichromate*and'aceticacid,

15 according to Example l, is effected. Subse- I quently the leather is rinsed andr'edyedjin the same bath. "After a second oxidation with bichr omate the leather is washedand Example}; 100 g. ofchamo'is-leather are thoroughly washed 'andjafterwards'ftreated p with a inixtureof 150cm. of 'a'hypochlorite of limesolu'tion of {P Be. in 'l'liter of water dur tlfil'minut '-i Th rerupqfift efi ea h trated sodium sulphide' fand ii "g. of hydiosul'fite'v are dissolved in 1259 com: of water of v 40 C. and the leather dyedjata temperature of 30-40C; ni -a closed apparatus; r After 20 minutes f dyeing the leather-is shortly rinsedin runnin water. Thereupon i the after oxidation wit bichromate and sulphuric acid is effected. Subsequently the leather is rinsed an'd treated with some soap I and yolkintheusualmanner. I,

In the foregoing example any other vat dyestuffs such as ciba red G (Colour Index No. 1226), ciba violet B (Colour Index'No.

40 1222) and so on may be used with similar What I claim is:

1. A process for dyeing chamois-leather, comprising the steps of treating chamoisleather with compounds yielding chlorine and dyeing same immediately after this treatment with dyestufis being reduced in' the dyebath.

2. A process for dyeing chamois-leather,

comprisin the steps of treating chamoisleather wit compounds yielding chlorine and dyeing same immediately after this treatment with sulphur dyes. v

3. A process for dyeing chamois-leather,

comprising the steps of treating chamoisleather with an aqueous solution of hypochlorite of lime and dyeing same immediately after this treatment with sulphur dyes.

In witness whereof I have hereunto signed my name this12th day of December, 1928.

HEINRICH BRUNNER. 

